The Isotope has two different Portsmouth ratings - DPN 74.3 for 1-up and DPN 77 for 2-up. Wind-dependent factors range from 2-4.5% speed difference. Except at the Nationals (where everybody races boat for boat), the Isotope fleet scores its "one-design" races on handicap between the two configurations. Now, there are two skippers (both usually sail singlehanded) who regularly dominate the fleet -- it is rare that another boat wins when they are racing. Aside from them, two-up boats do frequently correct up over one-up boats in the standings.

The Isotope is a 16-foot version of the 14-foot Cheshire, from which it was derived. Rumor has it that the builder made the first Isotope by cutting the Cheshire molds in half and lengthening them by 2 feet. The Cheshire was designed to be sailed single-handed. The Isotope was designed to be sailed by one or two people. Originally, it was raced 2-up quite a bit, but now is mostly 1-up.

There is no official manufacturer's sail plan, nor approved sailmakers. The class rules limit the boat to 185 sqft of soft sail, but allow you to divide it up between main and jib any way you like. One of the fleet members has a sail loft, and since we began sewing our own sails (maybe 15 years or so), we've pretty much gravitated to 44 sqft in the jib and 141 sqft in the main. Some sailors like a square-top mainsail, and others (including the designer) prefer a pin-top. The class as a whole decided that the performance difference between the two was small enough that we wouldn't differentiate between them. Either is permitted for one-design racing.

Regards,
Eric